Work on .beta.-lactam antibiotics has centered mainly on penicillins and cephalosporin compounds, both of which have bicyclic ring systems. Recently, new .beta.-lactam systems which maintain their antibiotic properties have been reported. Examples include nocardicin [J. Amer. Chem. Soc., 98, 3023 (1976)], which contains a monocyclic .beta.-lactam nucleus, clavulanic acid (Belgian Pat. No. 827,926), which has an oxygen-containing bicyclic .beta.-lactam nucleus, and bicyclic systems related to cephalosporins in which the sulfur atom has been moved to another position, [J. Amer. Chem. Soc., 99, 2353 (1977)] and has been replaced by oxygen or a methylene group [J. Med. Chem., 20, 551 (1977)]. These systems are not believed material prior art to the present invention.
I have now prepared a novel tricyclic .beta.-lactam system which contains additional nitrogen atoms; in particular, the 8,11-dioxo-1,3,7-triazatricyclo[7.2.0.0.sup.3,7 ]undecane and the 9,12-dioxo-1,3,8-triazatricyclo[8.2.0.0.sup.3,8 ]dodecane nuclei.